Photoelectric weft straightener



2 Sheets-Sheet 1 J7 sa Hafel'ff MER G. B. DUNN Fligl.

Dec. 27, 1949 PHOTOELECTRIC WEFT STRA'IGHTENER Filed April s, 1948Inventor George B. Dunn, bg wa Md.

His Attor'nag.

Dec. 27, 1949 G, B, DUNN PBo'roELEcTRIc wEFT STRAIGHTENER Filed April 8,1948 WEFT THREADS WEI-'T' THREADS WEFT THREADS Inventor'. George B.Dunn,

bg FA is Attorneg.

Patented Dec. 27, 1949 George B. Dunn,

General Electric Company,

New York Schenectady, N. Y., assignor to a corporation of ApplicationApril s, 194s, serial No. 19,677

(ci. afs-52) c claims. l

This invention relates to apparatus utilized in the manufacture ofwoven'material, more particularly to apparatus for straightening theweft of woven fabrics, i.' e., producing rectilinearity of the weftthreads and a perpendicular relationship between the weft threads andthe warp threads, and an object of this invention is the provision of asimple, reliable, inexpensive and improved device of this character.

A further object of the invention is the provision in apparatus of thecharacter described of a very simple, inexpensive and compact scanningdevice for detecting conditions of bow, skew and non-rectilinearity ofweft threads in woven material.

In carrying the invention into effect in one form thereof, means areprovided for projecting two beams of parallel light rays on a length ofWoven fabric so that the beams are directed toward opposite edges of thefabric. The direction of each beam is such that it makes an acute anglewith its own Orthographie or perpendicular projection on the plane ofthe fabric. Each of these perpendicular projections in turn makes anacute angle with a line in the plane of the fabric perpendicular to thewarp. On the opposite side of the fabric from the light sources aremounted two photoelectric cells. Each is mounted in a position toreceive light from a corresponding beam transmitted through the fabric.The cells are connected in corresponding arms of a bridge circuit. Whenthe weft threads are straight and are perpendicular to the Warp threads,the bridge is balanced and its output voltage is zero. If any skew orbow is present, the cells receive unequal amounts of light, and avoltage appears at-the output terminals. control a suitable device toposition the weft threads with respect to the warp threads to correctthe bow or skew.

For a better and more completel understanding of the invention referenceshould now be had to the following specification and to the accompanyingdrawing of which Fig. 1 is a simple diagrammatic sketch of an embodimentof the invention used to remove skew from a wovenfabric; Fig. 2 is asketch of a photoelectric scanning device; Figs. 3-8, inclusive, arediagrammatic sketches of different conditions of skew of the wovenmaterial which facilitate an under standing of the operation of theinvention; Fig. 9 is a diagrammatic sketch of an embodiment of theinvention which is useful in removing bow from This voltage is utilizedto a woven fabric; and Fig. 10 is a chart of diagram- 55 i on thematerial.

rected toward one edge of the material and the matic sketches whichillustrate the mechanical operation of the bow correcting device.

Referring now to the drawings, a length of woven material I is passedbetween a pair of mangle rolls 2, under an idler roll 3, over a cantingroll 4, under an idler roll 5 and thence into a tenter having endlesschains 6 and 1. These chains pass around end pulleys 8 and 8 which aredriven by suitable driving means such as an electric motor I0 to whichthey are mechanically connected. The tenter chains are thus driven atequal speeds.

The canting roll 4 is journaled for rotation in bearing blocks II andII'. These bearing blocks are connected through links I2 and I3 withnuts I4 and I5 which are threaded on the screw shaft I6 which may berotated in either direction by means of an electric motor I'I to whichit is connected through gearing I8. If the material approaching thetenter is skewed, the skew can be corrected by rotation of motor II inthe proper direction toelevate one end of the canting roll and to lowerthe opposite end.

The energization and direction of rotation of the correcting motor I'Iis controlled by skew detecting means which is illustrated as comprisinga pair of light sources I9 and 20 and a pair of photoelectric cells 2|and 22. Each source is provided with a suitable optical system forprojecting a beam of substantially parallel rays ol light. The source I9is mounted above one edge of the material and the source 20 is mountedabove the opposite edge. The sources are so positioned that they projectoppositely directed beams As shown, the beam 23 is dibeam 24 is directedtoward the opposite edge.

The beam 23 makes an acute angle 25 with its own orthographic projection23a on the plane of the material, and the beam 24 makes an acute angle26 with its orthographic projection 24a on the plane of the material.These angular relationships are illustrated in Fig. 2. The angles 25and'26 are substantially equal. The magnitude of the angle is determinedby the material. There is an optimum angle for each material. For somematerials the angle may be as small as twenty degrees and for others itmay be as large as sixty degrees and for still other materials it may besome angle between twenty and sixty degrees.

J Similarly, these projections 23a and 24a make acute angles 21 and 28with a line 29 in the plane of the material which is perpendicular tothe warp threads. The angles 21 and 28 are also substantially Aequal andtheir magnitude depends upon the material. There is an optimum angle foreach material. For most materials the value of this optimum angle isbetween twentyve degrees and sixty degrees.

The photoelectrie cell 2| is positioned on the axis of the beam 24 sothat it receives the light rays of this beam which are transmittedthrough the material. Similarly the photoelectric cell 22 is positionedon the axis of the beam 23 so that it receives the light rays of beam 23which are transmitted through the material.

The diameter of the beam will depend upon the dimensions of thephotoelectric cell. For most types of photoelectric cells Vcurrentlyavailable, a beam of 2-3" diameter may be employed. The beam willproduce an illuminated spot on the fabric which is elliptical in shape.

Each of the photoelectric cells 2| and 22 is connected in acorresponding arm of a bridge Ill of which the third and fourth arms arerepresented by the resistors 3| and 32. A direct voltage ofsubstantially constant value is supplied to the input terminals 30a and30h of the bridge from a source of regulated voltage which isrepresented by the two supply conductors 33 and 34. The output terminals30c and 30d of the bridge are connected to the input control terminals35a and 35h of a balanced electric valve amplifier 35. Direct voltage issupplied to the power input terminals 35e and 35d of the amplifier froma suitable source such as the supply conductors 33 and 34. The outputterminals 35e. 35i, 35g and 35h of the amplifier are connected to thecontrol input terminals 36a, 36h, 36e and 36d of a balanced poweramplier 36. Alternating voltage is supplied tc the power input terminals36e and 36j from a suitable source such as the two supply conductors 31and 38. The power output terminals 36g and 36h are connected to thearmature of the skew correction motor I'I.

When the bridge is balancedyi. e. when the photoelectric cells 2| and 22receive substantially equal amounts of light, the voltage across theoutput terminals 30c and 30d of the bridge is zero. Consequently thevoltage at the output terminal 35e and 35f of the ampliiier is equal tothe voltage at the terminals 35g and 35h. As a result both paths of thepower amplifier are equally energized. The current in each path isrectiiied half wave, and these currents are supplied to the motorarmature in opposite directions so that the net energization of themotor I1 is zero and the motor is at standstill. The magnitudes o! thebalanced output voltages of amplifier 35 are relatively low and theopposing circulating currents in the motor armature are correspondinglylow.

When the bridge becomes unbalanced in one direction, i. e. whenphotoelectric cell 2| receives more light than photoelectric cell 22receives, the current in one path of the power amplier is increased andthe current in the second path is reduced to zero, with the result thatthe motor rotates in a corresponding direction. Ii* the bridge becomesunbalanced in the reverse direction, the current in the second path isincreased and the current in the rst path is reduced to zero and themotor rotates in the reverse direction.

The appearance of the warp and weft threads when the material has noskew is illustrated in Fig. 3. If the light spot upon which the beamfalls is viewed from the position of light source I9. i. e. alongthe'axis of the beam 23, the appearance of the warp and weft threads inthe area within the spot illuminated by the beam is as illustrated inthe enlarged view shown in Fig. 4. Invother words, Fig. 4 illustratesthe "appearance of the warp and weft threads to the beam 24 when thematerial has no skew. It is clear that there are substantial spacesbetween the threads through which light is transmitted to thephotoelectric cell 2|. The appearance to the beam 23 is similar. Thespaces through which light is transmitted are equal for both beams andconsequently both cells 2| and 22 receive equal amounts of light withthe result that the bridge is balanced and the correction motor I1 is atstandstill.

If there is positive skew in the material, as illustrated in Fig. 5, theappearance of the warp and weft threads to the beam 24 is as illustratedin the enlargement of Fig. 6. The spaces through which light istransmitted are much reduced in size and correspondingly less light istransmitted4 through the material to the photoelectric cell 2|.

0n the other hand, if the material has negative skew, as illustrated inFig. '7, the appearance of the warp and weft threads to the beam 24 isas illustrated in Fig. 8. The spaces between the threads through whichlight rays of beam 24 are transmitted to photoelectric cell 2| arelarger than the spaces in the no skew condition illustrated in Fig. 4.Consequently more light is transmitted to the photoelectric cell 2| thanis transmitted during the condition of no skew.

To the beam 23 the appearance of the weft and warp threads duringconditions of positive and negative skew is the reverse of theirappearance to the beam 24. In other words, when the material haspositive skew, as in Fig. 5, the appearance of the threads to the beam23 is as illustrated in Fig. 8 and when the material has negative skewthe appearance of the threads to the beam 23 is as illustrated in Fig.6.

Thus, when the material has positive skew, the light received by thephotoelectric cell 22 is increased and the light received by thephotoelectric cell V2| is decreased. As a result the bridge 30 isunbalanced and the correction motor is energized for rotation in adirection to elevate the left-hand end of the canting roll 4, as viewedfrom the position of the mangle rolls 2, and to lower its right-handend. This movement of the canting roll retards thev left-hand selvage ofthe material and permits the right-hand selvage to advance. By left-handselvage is meant the selvage which is on the left of an observer lookingin the direction of travel of the fabric. This correcting operationcontinues until the skew is removed from' the material and the amountsof light received by photoelectric cells 2| and 22 are equal so that thebridge 30 is rebalanced and the correction motor is stopped. Similarlywhen the material has negative skew, the bridge becomes unbalanced inthe opposite direction electrically, and the correction motor |`l isenergized for rotation in a direction to elevate the righthand end ofthe canting roll and to lower the leithand end to retard the right-handselvage and advance the left-hand selvage. The operation continues untilskew is removed so that the bridge 30 is again balanced and thecorrection motor is stopped. It is not essential that the beams bedirected on diierent areas, as illustrated in Figs. 1 and 2. They may bedirected on the same area. This has the advantage that errors areeliminated which might arise if one beam falls on an area having a givendesign or color and the other beam falls on an area having a differentdesign or color.

terial passes over an idling roll 53, beneath the bowed roll 39, overthe bowed roll 39a and beneath an idling roll 54, as illustrated inFigs. 9 and 10.

The dotted line la in diagrams, a, b and c of Fig. 10 represents thewarp at the selvages and the full line Ib represents the warp at thecenter of the material. When the bowed rolls are in the positionsillustrated in Fig. 10a, the selvages travel the distance a between thebowed rolls, and the center travels the shorter distance b. Since theselvages must travel the longer distance in passing through thecorrector, they become advanced with respect to the center, and forwardbow in the material is corrected.

In Fig. 10b the distances a and b are equal. Therefore the selvages andthe center travel equal distances in passing through the corrector andno correction results This is the neutral position.

When the bowed rolls occupy the positions illustrated in Fig. 10c, thedistance b which the center of the material must travel is greater thanthe distance a which the selvages travel. Consequently the centerbecomes advanced with respect to the selvages and rearward bow iscorrected. Any other suitable bow eliminating device may be utilized inplace of the device 39. For example, the bow eliminator illustrated inFig. 1 of U. S. Patent 2,106,611, La Pierre, may be utilized if desired.

As shown in Fig. 9, the motor 42 is supplied from a power amplifier 44which is controlled by an amplifier 45. The amplier 45 in turn iscontrolled by a bridge 46. A photoelectric cell 41 is connected in onearm of the bridge and a photoelectric cell 48 is connected in anotherarm.

These photoelectric cells 41 and 48 together with light sources 49 and50 are mounted with respect to the fabric in the manner illustrated inFig. 9. -The source 49 projects a beam 5i which is transmitted throughthe fabric to the photoelectric cell 41. Similarly the light source 50projects a light beam 52 which is transmitted through the fabric to thephotoelectric cell 48. It will be noted that the beams 5| and 52 lie insubstantially parallel planes whichare perpendicular to the plane of thefabric as contrasted to the skew detecting device in which the projectedbeams lie in intersecting vertical planes.

When there is no bow in the fabric the appearance of the threads in theareas illuminated by the beams, as viewed from the positions of thelight sources, is as illustrated in Fig. 4. Consequently equal amountsof light from both beams are transmitted through the fabric to thephotoelectric cells 41 and 48. The bridge is balanced and the correctionmotor 42 is at standstill. If forward bow is present in the fabric, asillustrated in Fig. 9, the appearance of the threads in the areailluminated by beam 5|, as viewed from the location of the light source49, is as illus- .trated in Fig. 6. In other Words, the threads presenta closed-up appearance to the beam, and the amount of light transmittedthrough the fabric to the photoelectric cell 41 is correspondinglyreduced. On the other hand, the appearance of the threads in the areailluminated by the beam 52, as viewed from the position of light source50, is as shown in Fig. 8. That is to say.

the threads present an open appearance to the beam and a correspondinglyincreased amount of light from the beam is transmitted through thefabric to photoelectric cell 48.

As a result of the increased amount of. light received by photoelectriccell 48 and the decreased amount of light falling on photoelectric cell41, the bridge is unbalanced and the correction motor 42 is energized torotate the bowed rolls 39 and 39a toward the positions illustrated inF'ig. 10a to eliminate the forward bow from thevweft threads of thefabric. When the bowed lrolls '39 and 39a have been rotated a suillcientamount to eliminate the forward bow the amounts of light received byboth photoelectric cells are equal and the bridge is rebalanced. As aresult, the correction motor is deenergized and stopped.

Although in accordance with the provisions of the patent statutes thisinvention is described as embodied in concrete form and the principlethereof has been explained together with the best mode in which it isnow contemplated applying that principle, it will be understood that theelements shown and described are merely illustrative and that theinvention is not limited thereto since alterations and modications willreadily suggest themselves to persons skilled in the art withoutdeparting from the true spirit of this invention or from the scope ofthe annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. In a weft straightener for a length of material having warp threadsand weft threads, means for projecting on the fabric two beams of lightdirected toward opposite edges of the fabric, each of said beams makingan acute angle with its own perpendicular projection on the plane of thefabric and each of said projections making an acute angle with a line inthe plane of the fabric perpendicular to the warp, photoelectric meansresponsive to the difference in the amounts of said beams transmittedthrough said fabric, and means controlled by said photoelectric meansfor moving said weft threads with respect to said warp threads.

2. In a weft straightener for a length of material having warp threadsand weft threads.

means on one side of the plane of the fabric for projecting on thefabric two beams of light directed toward opposite edges of the fabric,each of said beams making an acute angle with its own perpendicularprojection on the plane of the fabric and each of said projectionsmaking an acute angle with a line in the plane of the fabricperpendicular to the warp, a pair of photoelectric devices mounted onthe opposite side of the plane of the fabric each in a position toreceive light from a corresponding one of said beams transmitted throughsaid fabric, and means controlled by said photoelectric devices forpositioning the weft threads perpendicular to said warp threads. 3. In aweft straightener for a length of material having warp threads and weftthreads, means for projecting on the fabric two beams of light directedtoward opposite edges of the fabric, each of said beams making an angleof between twenty and sixty degrees with its own perpendicularprojection on the plane of the fabric and each of said encara?projections making an angle of between twentyve and sixty degrees with aline in the plane of the fabric perpendicular to the warp, photoelectricmeans responsive to the difference in the amounts of said beamstransmitted through said fabric, and means controlled by saidphotoelectric means for varying the position of said weft threads withrespect to said warp threads.

4. In a weft straightener for a length of material having warp threadsand weft threads, means for projecting onthe fabric two beams of lightdirected toward opposite edges of the fabric, each of said beams makingan angle of between twenty and sixty degrees with itsA own perpendicularprojection on the plane of the fabric and each of said projectionsmaking an angle of between twenty-tive and sixty degrees with a line inthe plane of the fabric perpendicular to the warp, photoelectric meansfor measuring the amount of each of said beams transmitted through thefabric, and means controlled by said photoelectric means for varying theposition of said weft threads with respect to warp threads in responseto the dierence of said amounts of said beams transmitted through thefabric.

5. In a weft straightener for a length of material having warp threadsand weft threads, means for projecting on the fabric two beams of lightdirected toward opposite edges of the fabric, each of said beams makingan angle of between twenty and sixty degrees with its own perpendicularprojection on the plane of the fabric and each of said projectionsmaking an angle of between twentyfive and sixty degrees with a line inthe plane of the fabric perpendicular to the warp, photoelectric meansresponsive to the difference in the amounts of said beams transmittedthrough the fabric, and means controlled by said photoelectric means forpositioning said weft threads perpendicular to said warp threads.

6. In a weft straightener for a length of material having warp threadsand weft threads, means on one side of the plane of the fabric forprojecting on the fabric two beams of light directed toward oppositeedges of the fabric, each of said beams making an angle of betweentwenty and sixty degrees with its own perpendicular projection on theplane of the fabric and each of said projections making an angle or'between twentyve and sixty degrees with a line perpendicular to thewarp, a pair of photoelectric devices mounted on the opposite side ofthe plane ofthe fabric each in a position to receive light from acorresponding one of said beams transmitted through said fabric, andmeans controlled by said photoelectric cells in response to thediierence in. the amounts of light received by said photoelectric cellsfor positioning said weft threads perpendicular to said Warp threads.

GEORGE B. DUNN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,106,611 La Pierre Jan. 25, 19382,208,447 Berry July 16, 1940 2,219,213 Swain' Oct. 22, 1940 2,311,406Manseld et al Feb.'16, 1943 2,427,753 Vose et al. Sept. 23, 1947

